1. Field of the Invention
The present invention relates to a process for measuring the potential difference between a sample liquid flow delivered by pumping and a reference electrolyte, in which the sample flow is brought into contact with a reference electrode having a capillary channel extending substantially at right angles or transversely to the sample flow, one end of said capillary channel opening into said flow, wherein reference electrolyte, coupled to a reference element of the reference electrode, is fed into the other end of said capillary channel.
The invention also relates to an apparatus for measuring the ionic concentration in a sample liquid, as well as a reference electrode for performing the process and/or for the apparatus.
2. Description of the Related Art
In a known process for measuring the ionic concentration in a sample liquid (European Patent Applicaton Serial No. 0 105 434), the reference electrolyte is located in a tank above the channel, through which the sample liquid is pumped, and the interior of the tank is connected to a channel for the sample liquid via a capillary channel through which, under the influence of gravity, reference electrolyte passes out of the tank and into the sample channel. By means of a reference element immersed in the electrolytic tank, the potential difference between the sample liquid and the reference electrolyte is measured, in order to obtain a reference value for the potentials characterizing the ionic concentrations measured by means of the ion selective electrode or electrodes.
The known process suffers from the disadvantage that reference electrolyte passes permanently, i.e., also when no ionic concentration measurement is taking place, from the electrolytic tank into the sample channel via the capillary channel. This leads to a considerable reference electrolyte loss, unless the capillary channel has an extremely small cross-section. However, a small cross-section greatly increases the risk of the capillary channel becoming clogged. Then the electrolytic tank has to be emptied in the known arrangement for replacing the capillary body having the capillary channel. Finally, in the known system it is only possible to select a construction in which the electrolytic tank is positioned above the sample channel, because only then can the reference electrolyte pass by gravity into the sample channel.
In connection with a process for measuring the potential difference between a sample liquid and a reference electrolyte, the object of the invention is to reduce the reference electrolyte consumption, reduce the risk of clogging the electrolyte channel, and continuously remove from the reference electrolyte constituents gassing out, inter alia, in the vicinity of the reference element.